In Situ Growth of TiB2 Whiskers in TiB2-TiCx Matrix Powder

Abstract:

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The TiB2 whiskers were fabricated in TiB2/TiCx composites by the in-situ synthesis process. The phase composition, thermodynamics, weight loss and lattice parameters of the obtained phases were studied. The obtained TiB2 whiskers showed an aspect ratio of 10-20 and a diameter of 0.5-1.5 μm. The synthesized TiC was a non-stoichiometric phase with a lattice parameter of 4.274 Å. Most of the whiskers had the cylinder shape, whereas, a few whiskers showed a bead-necklace morphology. The growth mechanisms of TiB2 whiskers were governed by the solid-liquid-solid (S-L-S) mechanism and the particle-to-particle connection mechanism.

Abstract: In this paper, the SHS process using TiO2, Al and graphite powders has been performed successfully. The TiO2 : Al : C molar ratio was 3 : 4.2 : 2.8. XRD result shows the final product powder is Al2O3-TiC composite powder. The morphology and microstructure of the composite powder was also investigated.

Abstract: In-situ toughened TiC-Ti5Si3 composites were fabricated using reactive sintering of Ti and SiC via spark plasma sintering (SPS). The focus of this work on the content of TiC in final composites was different. The phase constituents and microstructures of the samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Fracture toughness at room temperature
was also measured by indentation tests. The results showed that the corporation of TiC greatly enhances the fracture toughness of TiC-Ti5Si3 composites.

Abstract: FeAl-TiB2 composites have been combustion synthesized from mixtures of
Fe, Al, Ti and B powders. When the powder mixture was heated in vacuum to
approximately 900 K, an abrupt increase in temperature was observed, indicating that
the combustion synthesis reactions occurred in the powder mixture. X-ray diffraction
analyses revealed that the combustion-synthesized sample consisted of only FeAl and
TiB2. Metallographic investigations using a scanning electron microscope revealed that
fine TiB2 particles were dispersed in FeAl matrix phase. As the volume fraction of the
TiB2 particles increased from 0.3 to 0.8 by controlling the powder mixture composition,
the average TiB2 particle size increased to 1 to 7 μm and the average Vickers hardness
of the composites increased from 800 to 1600. This method has been applied to the
fabrication of some other ceramic particle dispersed metal matrix composites such as
Fe-TiC and FeAl-TiC systems.

Abstract: Ti3SiC2 has been a spectacular material, as it combines many of the best properties of metals and ceramics. This new material has potential applications for fabrication of jet engines and in bonding phases. Microstructure can further enhance the mechanical properties, such as strength, wear resistance and chemical stability. In the current research the different starting powder systems were used to synthesize Ti3SiC2 by hot pressing. The contents of Si were controlled appropriately to obtain Ti3SiC2/TiC ceramic composites. Preliminary results indicated that the fracture toughness and strength were improved. The influences of TiC contents on the microstructure and mechanical properties were investigated and the fracture mechanisms of Ti3SiC2/TiC ceramic composites are discussed qualitatively.

Abstract: A high purity of Ti2AlC powder has been synthesized by pressureless sintering a mixture of Ti-Al-TiC-Sn (Sn as an additive) powders. Four recipes with different mole ratios of Ti-Al-TiC-Sn were examined at sintering temperature from 1400°C to 1480°C. A high purity of Ti2AlC powder can be obtained by sintering all these four recipes at temperature 1450°C for 10 min in an Ar atmosphere. The synthesis of Ti2AlC on this large mole ratio scale of starting materials is associated with the evaporation of Al at high temperature and the structure stability of Ti2AlC. From the X-ray diffraction analysis, a reaction path for the Ti2AlC formation is proposed. Scanning electron microscopy was also used to characterize the samples.